The present invention relates to an injection molding process and an injection molding machine which makes part ejection easier.
It is highly desirable to reduce the number of parts in an injection molding machine and hence the overall cost and complexity of such machines. It is also desirable to enable the more efficient use of space and provide for a simplified operation.
Previously, it has been known to simplify injection molding machines by providing a machine which has a first mold half affixed to a stationary mold platen and a rotatable turret block which carries a plurality of mating, second mold halves that can be brought into alignment with the first mold half during the molding cycle. Such injection molding machines are illustrated in U.S. Pat. Nos. 5,728,409; 5,750,162; and 5,817,345, all assigned to the assignee of the instant application, and all incorporated by reference herein. It is also known that such injection molding machines can be vertically oriented so that the turret block moves along a vertical axis towards and away from the first mold half.
It is also known in the prior art that advantages can be gained by providing an improved tiebar construction in which at least two tiebars connect a stationary platen with a movable platen, a stroke cylinder within at least two of the tiebars is operative to move the platens from an open to a closed position and from a closed to an open position, and means are carried by the at least two tiebars to engage a releasable clamping means for clamping the two platens together in the closed position. Such a tiebar construction is shown in co-pending U.S. patent application Ser. No. 09/070,598, filed Apr. 30, 1998, entitled TIEBAR STRUCTURE FOR INJECTION MOLDING MACHINE, to Galt et al. (98-205), which is also assigned to the assignee of the instant application and which is incorporated by reference herein.
Recently, turret block injection molding machines have been further improved by the incorporation of a frameless electric drive for rotating the turret block. Such an injection molding machine is shown in co-pending U.S. patent application Ser. No. 09/072,310, filed May 4, 1998, entitled FRAMELESS ELECTRIC DRIVE FOR TURRET MACHINE, by Looije et al., now U.S. Pat. No. 6,024,558, which is also assigned to the assignee of the instant application and which is incorporated by reference herein.
Despite these improvements, there remains a need for an injection molding machine and an injection molding process which enables molded parts to be more easily ejected and which allows said ejection to occur at any time during a molding cycle.